On Tuesday, the studio filed a complaint in Los Angeles Superior Court against Jake LaMotta, the 90-year-old former boxing champion whose life was portrayed by Robert De Niro in the 1980 Martin Scorsese-directed classic, as well as RBII Production, which is said to be nearing completion of principal photography of a low-budget Raging Bull sequel.

According to the complaint, the sequel is based on a 1986 book co-written by LaMotta.

MGM claims that under an original agreement in 1976 to acquire rights to LaMotta's first autobiography, LaMotta and co-writer Peter Savage were contractually obligated to present terms and conditions on which they would sell rights to any sequel.

The lawsuit says that LaMotta and Savage only had the right to sell the sequel to another company if Chartoff-Winkler Productions, an entity acquired by MGM, didn't accept the offer, and even then, only for terms no less favorable than what had been offered to MGM.

MGM says that LaMotta didn't comply, and now after selling rights to Raging Bull II: Continuing the Story of Jake LaMotta, the sequel is nearly complete despite MGM's demands that they desist from producing the film. According to IMDb, Raging Bull 2 is scheduled to come out next year and star William Forsythe, Joe Mantegna and Paul Sorvino.

LaMotta reportedly is not happy about the development.

“How can you fight a company that big?” he told the New York Post, adding, “All of these business things, I don’t bother with it because I’m not capable, physically or mentally, because I don’t hear so good.”

LaMotta might not feel in shape to do battle, but Raging Bull rights have been in dispute for several years, even before MGM's latest strike Tuesday.

The heir of Peter Savage (a pseudonym for Peter Patrella) has been attempting to grab back the copyright on Raging Bull, arguing that the rights reverted after the original term expired.

In 2009, Patrella's daughter filed a lawsuit against MGM and 20th Century Fox that sought a declaration of ownership as well as $1 million in copyright infringement damages.

A judge dismissed the lawsuit because the plaintiff had waited too long to bring the case, and now the dispute is on appeal before the 9th Circuit.

MGM believes its contractual hold over the Raging Bull property is still operative and is now alleging breach of contract, tortious interference and unfair competition. MGM demands a rescission of the agreement by which LaMotta granted rights to Raging Bull II, monetary damages and a preliminary and permanent injunction against distribution and promotion of the sequel.